The invention relates to a multi-functional device for a print cartridge of an ink jet printer.
Thermal ink jet printers use cartridges containing printheads having heating elements on a semiconductor substrate for heating ink so that the ink is imparted with sufficient energy to cause the ink to be ejected through a nozzle hole in a nozzle plate attached adjacent to a semiconductor printhead substrate. The nozzle plate typically consists of a plurality of spaced nozzle holes which cooperate with individual heater elements on the substrate to eject ink from the cartridge toward the print media. The number, spacing and size of the nozzle holes influences the print quality. Increasing the number of nozzle holes on a printer cartridge typically increases the print speed without necessarily sacrificing print quality. However, there is a practical limit to nozzle bole or orifice size and to the size of the semiconductor substrate which can be produced economically in high yield. Thus, there is a practical limit to the number of corresponding nozzle holes which can be provided in a nozzle plate for a printhead.
For color printing applications, the three primary colors of cyan, magenta and yellow are used to create a palette of colors. Typically, all three colors are provided by a single printhead or chip and a single nozzle plate attached to the printhead. However, this results in relatively slow print speeds because each color swath is small due to the size of the portion of chip being used for that color. In order to obtain suitable substrate production yields, the printheads or chips cannot be large enough to contain the same number of energy imparting devices as would be found on individual printheads for each color.
In an effort to increase printing speed, separate printheads and nozzle plates for each color are attached to separate cartridges. In such a design, the number of nozzle holes per color is maximized for high quality, higher speed printing. However, it is extremely difficult to maintain an alignment tolerance of a few microns between the printheads when using separate cartridges for each color.
While locating multiple individual substrates of a conventional size on the same cartridge may allow a relatively faster printing rate, such a design contributes to significantly increasing the printhead and cartridge temperatures because of the greater number of energy imparting devices located on the printhead and the desire to eject the ink from the cartridge at a faster rate. Increased printhead and cartridge temperatures cause problems with ink ejection due to viscosity changes in the ink resulting in oversize ink droplets and well as premature ejection of ink from a nozzle hole. Higher temperatures may also contribute to air bubble formation in the ink chambers of the printhead which air bubbles inhibit ink droplet formation. Plugging of the nozzle holes by a build up of ink decomposition products adjacent the nozzle holes may also be a problem caused by higher printhead and cartridge temperatures. Furthermore, without adequate temperature control, dimensional changes in the printhead are not predictable making it difficult to achieve the desired dot placement which adversely affects print quality.
Various materials and methods have been proposed for removing heat from the printhead substrates and cartridges. For example, U.S. Pat. No. 5,084,713 to Wong describes flowing ink from the reservoir through a support panel for the heater substrate to cool the printhead. Such a design requires an adequate flow of ink to the printhead in order to remove sufficient heat therefrom.
U.S. Pat. No. 5,066,964 to Fukuda et al. describes the use of flowing ink in combination with a heat capacity member to remove ink from the printhead in order to cool the printhead. U.S. Pat. No. 5,657,061 to Seccombe et al. describes the use of a heat exchanger in the ink flow path to cool the ink and thus cool the printhead as the ink flows to the substrate. Other methods of removing heat include the use of a heat pipe and blower as described in U.S. Pat. No. 5,451,989 to Kadowaki et al.
Conventionally, materials which exhibit a low thermal expansion coefficient have been used to provide suitable heat removal without sacrificing print quality. Materials having low thermal expansion coefficients do not typically expand or contract a sufficient amount to affect printer operation and thus print quality. The materials also enable easier and cheaper printhead and cartridge fabrication techniques since expansion and/or contraction of the components and electrical connections therebetween is minimized. However, such materials are typically made from exotic composite materials such as metal-ceramic mixtures, carbon fiber, or graphite composites which are costly to make and use in such applications.
An object of the invention is to provide an improved ink jet printer cartridge structure.
Another object of the invention is to provide a single print cartridge containing multiple chips or semiconductor substrates thereon for color printing.
Still another object of the invention is to provide a method for improving print quality in a multi-color print cartridge.
A further object is to provide a multi-color print cartridge for a thermal ink jet printer which provides improved print quality at a relatively lower cost than conventional print cartridges.
Another object is to provide a multi-color print cartridge which contains a device for precisely locating chips for each of the primary colors.
Still another object of the invention is to provide a multi-function print cartridge structure which provides efficient heat removal from the chips and a locating surface for aligning multiple chips thereon.
Yet another object of the invention is to provide a rigid, substantially planar surface for accurately mounting and aligning the semiconductor substrates, nozzle plates and electrical tracing thereon.
With regard to the above and other advantages, the invention provides an ink jet print cartridge structure containing one or more semiconductor substrates mounted on a substrate holder, the substrate holder having a top surface having a perimeter and containing one or more substrate locator wells, each well having a plurality of well walls and a well base, each well base including at least one ink feed slot therein, the holder also having side walls attached to the top surface along the perimeter thereof, wherein one or more of the side walls contain fins for convectively removing heat from the substrate carrier. It is preferred that the substrate holder be molded, cast or machined for precision and it is particularly preferred that the substrate holder be made substantially of metal.
In another aspect, the invention provides a method for making a print cartridge for a multi-color thermal ink jet printer which comprises providing multi-function substrate carrier and ink reservoir body, the substrate carrier having a top surface containing one or more substrate locator wells each well having well walls, a well base and at least one ink feed slot in each well base, side walls attached to the top surface along the perimeter thereof wherein one or more of the side walls contain fins for heat removal from the substrate carrier and at least two alignment devices adjacent one of the side walls for precisely attaching the substrate holder and reservoir body to a printer carriage, mounting two or more semiconductor substrates containing a plurality of resistive elements and attached nozzle plates in the wells adjacent the well base of the substrate carrier, attaching a TAB circuit or flex circuit to the semiconductor substrates and the top surface of the substrate carrier for energizing the resistive elements on the substrates and inserting one or more ink containers into the ink reservoir body.
Yet another aspect of the invention provides a nose piece for an ink jet printer cartridge, the nose piece comprising a machined, molded or cast, substantially metal structure having a top surface containing one or more substrate locator wells each well having well walls, a well base and at least one ink feed slot in each well base, side walls attached to the top surface along the perimeter thereof wherein one or more of the side walls contain fins for heat removal from the substrate carrier, a plurality of slots along the perimeter of the side walls for precisely attaching the substrate holder to an ink reservoir body and at least two alignment devices adjacent one of the side walls for precisely aligning the substrate holder and reservoir body to a printer carriage, wherein the metal is selected from the group consisting of aluminum, beryllium, copper, gold, silver, zinc, tungsten, steel, magnesium and alloys thereof.
The apparatus and method of the invention provide the means for effectively removing heat from the printhead and print cartridge thereby improving printer performance, operation and reliability. Adequate cooling of the cartridge components is particularly important for cartridges containing multiple printheads, particularly with the increased number of energy imparting devices on each printhead substrate and with the increased firing speed of the energy imparting devices.
By providing a nose piece or substrate carrier and/or ink reservoir body for inserting separate ink containers therein, materials having more effective heat removal than plastic may be used for the nose piece and/or reservoir body. Such materials include not only exotic composite materials such as those containing a high content of carbon fibers or graphite and metal-ceramic materials, but also relatively inexpensive metals such as aluminum, zinc, copper and alloys thereof which possess relatively high thermal conductivities and having relatively high thermal expansion coefficients. Such metals and alloys may be used to provide an effective heat transfer medium for cooling the print cartridge components.